Old CM4228 with Hollands Horiz Harness

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Old CM4228 with Hollands Horiz Harness

Old CM4228 with Hollands Horizontal Harness (HHH) replacing the Original Harness analyzed using 4nec2.
Dimensions of HHH OPTIMIZED using nikiml's Python Control Scripts were the WIDTH of the Feedline (Gap)
and X-Axis SEPARATION from the Center of the Bowties, similar to 2x2 4-Bay (H4) as well as the
Vertically Stacked 4-Bay Antenna designs. Bowtie Tine Separation and Sweep were also Optimized.

When surveying the "terrain", I noticed that original CM4228a model (posted by Ken Nist on HDTVPrimer)
did NOT include the two 1.25-in Diameter Tubes which support the Bowtie/Feedline structures.
Since HHH could intersect or be influenced by the close proximity, I added Vertical Tubes to MY
CM4228 (8.0x8.0) model, which uses MY ACTUAL MEASUREMENTS. This significantly improved SWR and the
low frequency roll-off problem found in Ken Nist's model, as shown in Charts. To facilitate Apples-to-Apples
comparisons, I also reran the RF Combiner Mod version after adding the Vertical Tubes.

Two HHH versions were Optimized to determine the "best":
ALT#1 - HHH is In-between Bowties and Reflector, providing best UHF & Hi-VHF performance.
ALT#2 - HHH is In-front of Bowties, included here in case a user prefers that arrangement.

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ALT#1 - Optimized Dimensions for HHH In-between Bowties and Reflector:
Tine Sep = 4.0-in, NO Sweep. Gap = 1.3-in (about 1.25-in) = Separation between Feedlines,
Xh = - 1.12-in = Separation between Feedlines and Center of Bowties. Diagonal Wire Lengths,
Harness to Feedline = 2.69-in (Top-Left & Bottom-Right) AND = 1.67-in (Bottom-Left & Top-Right).
Yinner = 11.71-in = Y-Axis Distance from Harness to INNER Bowtie Feedline (Top-Left & Bottom-Right).
Youter = 11.71-in = Y-Axis Distance from Harness to OUTER Bowtie Feedline (Bottom-Left & Top-Right).

Each HHH wire Length = 16.07-in + 2 x 0.715-in eyelets on ends = 17.5-in. TOTAL.
Whatever lengths is needed to get around obstacles near attachment screws are to be subtracted
from Harness Length along Y-Axis, maintaining 1.12-in Separation between Harness and Bowties.

UHF Raw Gain = 14.8 to 14.7 to 17.8 dBi, F/B & F/R Min = 21.9 dB and SWR (300-ohms) Under 2.1.
Hi-VHF Raw Gain = 5.0 to 10.4 dBi, Peaky on Ch9, Hi-VHF F/B & F/R Ratio Minimum = 10.3 dB
and SWR (300-ohms) under 5.1.
Still, these are significant improvements over the AS-SHIPPED CM4228 version.

Views with Reflector Removed are included to facilitate seeing the HHH.

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ALT#2 - Optimized Dimensions for HHH In-Front of Bowties:
Optimum Tine Sep = 3.125-in, NO Sweep. Gap = 0.92-in (about 1.0-in) = Separation between Feedlines,
Xh = -2.21-in = Separation between Feedlines and Center of Bowties. Diagonal Wire Lengths,
Harness to Feedline = 3.18-in (Top-Left & Bottom-Right) AND = 4.19-in (Bottom-Left & Top-Right).
Yinner = 12.9-in (about 13.0-in) = Y-Axis Distance from Harness to INNER Bowtie Feedline (Top-Left & Bottom-Right).
Youter = 12.9-in (about 13.0-in) = Y-Axis Distance from Harness to OUTER Bowtie Feedline (Bottom-Left & Top-Right).

Each HHH wire Length = 20.27-in + 2 x 0.74-in eyelets on ends = 21.75-in. TOTAL.
Whatever lengths is needed to get around obstacles near attachment screws are to be subtracted
from Harness Length along Y-Axis, maintaining 2.21-in Separation between Harness and Bowties.

UHF Raw Gain = 13.5 to 17.0 dBi, F/B & F/R Min = 19.9 dB and SWR (300-ohms) Under 2.6.
Hi-VHF Raw Gain = 8.7 to 6.4 to 9.3 dBi, but 2.5 dB NULL on Ch9 could be a Problem
Hi-VHF F/B & F/R Ratio Minimum about 10 dB, Except for DIP on Ch9 and SWR (300-ohms) = 24.2 to 2.3 to 4.4.
Although significantly lower Gain than ALT#1, these are small improvements over AS-SHIPPED CM4228 version.

Date(s): 3 Jul 2014. Album by holl_ands. 1 - 54 of 54 Total. 5189 Visits.

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